1. Field of the Invention
The present invention relates to an improvement in an arch type strapping machine. In particular, it relates to a band guide for a strapping machine in which the band guide is constituted by a few kinds of structural elements each having the same shape and the same size to obtain various sizes of band guide, and in which the structural elements are combined depending on the size of articles to be packed, whereby the band guide can be produced in a large scale production economically.
2. Discussion of the Background
Conventional arch type strapping machines have been of a one-piece body type. FIGS. 14 and 15 show a conventional band guide 151 for winding a band B around an article to be packed wherein the band B is supplied through a band feeding rollers driven by a driving unit. The band guide is constituted by an elongated one-piece body having substantially a ]-shaped groove.
The band guide was formed by, for instance, extruding synthetic resin or metal to be an elongated one-piece body having a ]-shaped groove in cross section. Then, the one-piece body was cut at an appropriate length, and a cut piece was subjected to bending operations whereby a band guide having a predetermined size can be formed.
In conventional techniques, the strapping machines of various sizes were manufactured depending on the sizes of articles to be packed. Accordingly, it was necessary to chose the size, i.e. the entire length and the shape of band guides so as to meet the sizes of the strapping machines. The production of various sizes of band guides depending on strapping machines having various sizes made working processes complicated. Further, since the band guides were not interchangeable between the strapping machines of various sizes, large-scale production was impossible and manufacturing costs were increased.
Further, the conventional band guides had a disadvantage that the removal of a band from the groove of a band guide at the time of returning the band was not smooth. Namely, since the conventional band guide was prepared by bending an elongated one-piece body, there was difficulty in removing the band from the groove at the time of returning the band. Specifically, the band guide supported by an arch unit 50 by means of springs in a movable manner is moved as a whole at the time of removing the band as shown in FIG. 15. Since, the band guide is formed of an elongated one-piece body, the entirety of the band guide tends to move as a whole at the time of the removal of the band B. Accordingly, the band B is not successively removed from the band guide, and a portion of the band B received in an upper band guide portion falls at the same time of the removal of the band at a lower band guide portion. This may result in twisting of the band when the band is wound around the article. Further, the movement of the band guide having a large weight can not be smooth because it has a large force of inertia. Therefore is therefore a large amount of friction generated between the band B and an inner side surface of the groove when the band is removed. Accordingly, a large force is required to return the band B. As a result, an excessive force acts on the returning rollers, and working efficiency decreases.